A motley crew of socialites, rappers and reality stars collided at a combined bash for 50 Cent’s SK Energy drinks and DJ Pauly D’s Remix cocktail concoctions Thursday. The burgeoning beverage entrepreneurs’ “Rock the Rooftop” party at Hudson Terrace brought out guests ranging from Lauren Remington Platt and Alexandra Lebenthal to Renee Graziano and Melissa Gorga to Carson Kressley. A spy said Fitty was introducing himself to well-wishers under his real name, Curtis Jackson. “He’s become more serious as a businessman,” said one impressed spy of Jackson’s SK empire. But another guest was surprised at the number of tunes by rival rapper Jay-Z that blared over the sound system.